DNA replication begins at the origin of replication site. Helicase unwinds the DNA double helix by breaking the hydrogen bonds between base pairs. DNA polymerase then reads the unwound DNA strands in the 3’ to 5’ direction and uses each strand as a template to assemble new complementary strands. This results in two identical copies of the original DNA. Okazaki fragments are produced on the lagging strand since DNA synthesis can only occur in the 5’ to 3’ direction. Ultimately, DNA replication precisely duplicates the genome so that each daughter cell formed during cell division contains an identical copy.

1. DNA
Replication
Mackenzie Atcheson

2. DNA Replication begins in
the Origin of Replication.
This is Called the
Replication Fort.

3. Adenine
5’
5’

4. Adenine
5’
Thymine
5’

5. Adenine
5’
Thymine
Cytosine
5’

6. Adenine
5’
Thymine
Cytosine
Guanine
5’

7. Adenine
5’
3’
Thymine
Cytosine
Guanine
3’
5’

8. Adenine
5’
3’
A
Thymine
Adenine
A purine
base, that is the
constituent
involved in base
pairing with
thymine in DNA
and with uracil
in RNA.
A
Cytosine
Guanine
3’
A
5’

9. Adenine
5’
A
T
3’
Thymine
T
A
A
T
Thymine
a pyrimidine
base that is one
of the four bases
coding genetic
information in
the
polynucleotide
chain of DNA
Cytosine
Guanine
3’
5’

10. Adenine
5’
A
T
3’
Thymine
Cytosine
a pyrimidine
base that codes
genetic
information in
the
polynucleotide
chain of DNA or
RNA
C
T
A
Cytosine
C
Guanine
3’
A
T
5’

11. Adenine
5’
A
T
3’
Thymine
G
T
Guanine
a purine base
that codes
genetic
information in
the
polynucleotide
chain of DNA or
RNA
C
A
Cytosine
C
G
Guanine
3’
A
T
5’

12. Adenine
5’
A
T
3’
Thymine
G
T
DNA
Polymerase
Reads
DNA
In
The
3’-5’
Direction.
C
A
Cytosine
C
G
Guanine
3’
A
T
5’

13. 5’
A
T
G
C
T
A
C
G
A
T
Helicase
The first step
of DNA
replication is
unwinding or
unzipping the
DNA. Helicase
is the enzyme
that unzips the
DNA.
5’
Hydrogen
Bonds between
the base pairs
are broken.

14. 5’
A
T
G
C
T
A
C
G
A
A molecule of DNA
Polymerase attaches
to one strand of the
DNA and moves in
the 3’ to 5’ direction.
T
5’

15. 5’
A
T
G
C
T
A
C
G
A
A molecule of DNA
Polymerase attaches
to one strand of the
DNA and moves in
the 3’ to 5’ direction.
T
5’
This is used as a
template for
assembling a leading
strand of nucleotides
and reforming the
double helix.

16. 5’
A
T
G
C
T
A
C
G
A
DNA synthesis
can only occur in
a 5’ to 3’
direction.
T
5’

17. 5’
A
T
G
C
T
A
C
G
A
DNA synthesis
can only occur in
a 5’ to 3’
direction.
T
5’
Another form of
DNA polymerase
binds to the other
strand.

18. 5’
A
T
G
C
T
A
C
G
A
This molecule
must synthesize
discontinuous
segments of
polynucleotides
T
5’

19. 5’
A
T
G
C
T
A
C
G
A
This molecule
must synthesize
discontinuous
segments of
polynucleotides
T
5’
These are called
Okazaki
Fragments.

20. There are
now two
identical
copies of the
DNA.
Sugar
Phosphate
Backbone
BASE PAIRS
Thymine—Adenine
Guanine—Cytosine

21. DNA
Replication
occurs in the
“S” phase of
the interphase
in mitosis.
Sugar
Phosphate
Backbone
BASE PAIRS
Thymine—Adenine
Guanine—Cytosine

22. THE
END